Apparatus for pyrolytic treatment of solid waste materials to form ceramic prills

ABSTRACT

Solid waste material is disposed of and a portion thereof converted into valuable refractory prills by use of a reactor having a substantially vertical pyrolysis chamber, a refuse charging inlet and a combustible gas outlet in the upper region thereof and a molten refractory material outlet in the lower region thereof. The molten refractory material withdrawn from the chamber is prilled to form ceramic beads. Gas-feed means charges an oxygen-rich gas into the chamber under pressure at a plurality of vertically spaced points along the length thereof so as to produce combustion of the waste organic components and generate heat. The charge is controlled to maintain a plurality of different temperature zones along the length of the chamber so as to effect incomplete combustion of the waste organic component and form a combustible gas and an organic-free molten refractory material. Preferably the gas-feed means includes a substantially vertical core member with the chamber, for receiving and channeling the oxygen-rich gas through conduits therein, and the distribution of the oxygen-rich gas among the various conduits is controlled by temperature sensors located within the various temperature zones. 
     The solid waste material may be compacted prior to being charged through the refuse charging inlet. The combustible gas may be processed to recover tars, and it may be burned to generate heat for producing power. The solid waste material contains as minimum weight values about 2.0 per cent of glass and ceramics, 18.0 per cent of paper products, 3.0 per cent of metals and 6.0 per cent of food waste and other organic materials.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 542,027filed Jan. 16, 1975, which in turn is a division of U.S. applicationSer. No. 321,449 filed Jan. 5, 1973, now issued as U.S. Pat. No.3,926,582 granted Dec. 16, 1975.

BACKGROUND OF THE INVENTION

Techniques have previously been proposed for the economic disposal ofurban refuse by conversion to useful products intended for sale tooffset the cost of collection and treatment. Treatment of refuse in sucha manner to produce a refractory product through pyrolytic techniqueshas been disclosed in the prior art. Various of these techniques haveinvolved the pretreatment of the refuse to provide separate fractions,the introduction of preheated oxygen-rich gas into a reactor either fromthe base or sidewalls, application of external heat to effect pyrolysis,and other expensive or inefficient techniques.

It should be understood that, for the purposes of this specification,except where the context clearly indicates otherwise, the term"pyrolysis" is to be comprehended as being used in a broad senseincluding the drying of refuse, the charring of incombustible organicmaterial and the formation of inorganic oxides as well as thedecomposition of organic material into volatile gases.

The term "solid waste material" as used herein, refers to theheterogenous mixture of organic wastes (including paper, food wastes,natural and synthetic rubbers, organic yard wastes, etc.) and inorganicwastes (including tin cans, glass, ceramics, etc.) conventionallyobtained by urban refuse collection systems. It will be furtherdescribed hereinafter.

Because of the low value of the refractory product obtained by prior actprocesses, such techniques have been of limited commercially feasibilityand must operate at a very high level of efficiency. For example, thepyrolysis of the refuse should be closely controlled to insure that theorganic components of the refuse are removed as volatiles so as tomaximize both the purity of the refractory material being produced forsale and the percentage of the total available energy of the refusebeing utilized by the system.

Existing pyrolysis reactors tend to be bulky in size to accommodate thelarge volumes of waste material to be processed and have elaboratemechanisms to seal the reactor during charging to preclude escape of thereactor gases. The size of these reactors and the need for elaboratesealing mechanisms obviously contribute to their high initial cost andhigh cost of operation.

Accordingly, it is an object of the present invention to provide a novelapparatus for disposing of solid waste material and obtainingsubstantially pure refractory material prills; as a product thereof.

It is also an object of the invention to provide such an apparatus whichis highly economical as a result of the relatively low operating costsand high utilization of components.

It is another object to provide such an apparatus which enables closecontrol of the pyrolytic treatment to obtain the maximum availableenergy from the refuse.

It is a further object to provide such an apparatus for producingvaluable substantially pure ceramic prills of controllable size as aproduct of the waste disposal technique.

It is a final object to provide such an apparatus which is smaller thandevices of comparable capability and which does not require elaboratesealing mechanisms.

SUMMARY OF THE INVENTION

It has been found that the foregoing and related objects may readily beobtained by a method for disposing of and converting solid wastematerial in which there is provided a substantially vertical pyrolysischamber and solid waste material having organic and inorganic componentsis charged into the upper region of the pyrolysis chamber. The solidwaste material contains as minimum weight values about 2.0 per cent ofglass and ceramics, 18.0 per cent of paper products, 3.0 per cent ofmetals and 6.0 per cent of food waste and other organic materials. Anoxygen-rich gas is charged under pressure into the chamber at aplurality of vertically spaced points along the length thereof so as toproduce combustion of the organic components and generate heat. Thecharge of the oxygen- rich gas at the plurality of points is controlledto maintain a plurality of different and downwardly increasingtemperature zones along the length of said chamber so as to effectincomplete combustion of the organic component and form a combustiblegas in the upper zones and to meet and oxidize the inorganic componentsof said solid waste material into an organic-free molten refractorymaterial in the lowermost zone, the temperature of the molten refractorymaterial at the lower region of the pyrolysis chamber being at leastabout 1075° Centigrade. The combustible gas is removed from the upperregion of the pyrolysis chamber and the molten refractory material isremoved from the lower region thereof. A molten refractory material isprilled to form ceramic prills which are recovered as a product of theprocess.

Preferably the oxygen-rich gas is introduced into the chamber about thevertical axis thereof and discharged outwardly into the chamber at theaforementioned points, this being most readily accomplished by providinga coaxial core within the chamber and introducing the oxygen-rich gasinto the core and discharging it outwardly therefrom. Desirably theoxygen-rich gas is introduced in the upper region of the core and passeddownwardly therethrough.

The temperatures prevailing in the zones are sensed and the discharge ofthe oxygen-rich gas at the aforementioned points is modified in responsethereto to control the combustion of organic components therein. Thusthe temperature of each zone is substantially independently controlledthrough regulation of the oxygen-rich gas discharged at each of theaforementioned points, the oxygen-rich gas itself being preheated to acontrolled temperature.

The discharge of the oxygen-rich gas is controlled to maintain an upperzone of 375° - 750° Centigrade, and preferably about 425° - 600°Centigrade; a middle zone of about 550° - 1075° Centigrade, andpreferably about 700° - 925° Centigrade: and a lower zone of about1075° - 1650° Centigrade, and preferably about 1100° - 1300° Centigrade.The combustible gas is removed at a temperature of about 250°-550°Centigrade, and preferably about 275°-425° Centigrade. The control iseffected by discharging into each zone about 45 to 60 percent by weightof the total of oxygen-rich gas being discharged, preferably about 10-25percent by weight into the upper zone, 15-35 percent into the middlezone and 25-60 percent into the lower zone.

The waste material is compacted prior to charging, with the chamberpreferably being sealed between intermittent charges. The removedcombustible gas may be combined with oxygen-rich gas and substantiallycomplete combustion thereof effected to heat a fluid medium, preferablythe oxygen-rich gas to be discharged into the chamber.

The apparatus for disposing of solid waste is comprised of a reactorhaving a shell providing a substantially vertical pyrolysis chamber, acharging inlet and a gas outlet in the upper region thereof and a liquidoutlet in the lower region thereof. Also provided are means for chargingsolid waste material having organic and inorganic components throughsaid charging inlet and gas-feed means for discharging an oxygen-richgas into the chamber under pressure at a plurality of vertically spacedpoints along the length thereof so as to produce combustion of the wasteorganic components and generate heat. Control means regulate thedischarge of the oxygen-rich gas at the aforementioned points tomaintain a plurality of different temperature zones along the length ofsaid chamber, so as to effect incomplete combustion of the waste organiccomponent and form a combustible gas and an organic-free moltenrefractory material. Completing the apparatus is a prilling chamberwherein the molten refractory material is converted into ceramic prills.

In a preferred embodiment, the gas-feed means includes a substantiallyvertical coaxial core member within the said chamber to receive theoxygen-rich gas, the core member having ports adjacent theaforementioned vertically spaced points for discharge of the oxygen-richgas therethrough. This may readily be accomplished by providing thegas-feed means with a plurality of substantially vertical coaxialconduits of differing length in said core member communicating with thecore member ports, means for introducing the oxygen-rich gas into theconduits and discharging the oxygen-rich gas from the conduits into thechamber through the communicating core member ports. Desirably the meansfor introducing the oxygen-rich gas into the conduits is disposedadjacent the upper ends of the conduits for communication therewith, andthe core member ports are disposed adjacent the lower ends of theconduits for communication therewith. The chamber is additionallyprovided with vertically spaced thermal sensors, the control means beingresponsive to the thermal sensors for controlling the oxygen-rich gasbeing discharged at the aforementioned points.

In a preferred embodiment the apparatus additionally includes acombustion chamber and heat exchange means therein for passage of afluid medium therethrough. Also provided are means for conducting theremoved combustible gas from the gas outlet to the combustion chamber,means for admixing oxygen-rich combustion gas with the combustible gas,and means for combusting the removed combustible gas and the oxygen-richcombustion gas in the combustion chamber to heat a fluid medium in theheat exchange means. Desirably the combustion chamber additionallyincludes means for passing oxygen-rich gas through the heat exchangemeans as the aforementioned fluid medium and a conduit from the heatexchange means to the gas-feed means, whereby the heat produced by thecombustion heats the oxygen-rich gas prior to the discharge thereof intothe pyrolysis chamber. In an alternative embodiment, instead of acombustion chamber there may simply be provided a heat exchanger, aconduit from the gas outlet to the heat exchanger for passing theremoved combustible gas therethrough and a conduit from the heatexchanger to the gas feed means whereby the oxygen-rich gas may bepassed therethrough in heat exchange contact with the combustible gasfor heating prior to its discharge into the pyrolysis chamber.

Additional features of the system may include a tar separation systemcomprised of a tar separating chamber, liquid spray means therein forspraying the removed combustible gas with liquid to condense tarstherein and means for removing condensed tars therefrom. Burner meansadjacent the base of the pyrolysis chamber may also be provided.Desirably the bottom end of the core member has a downwardly openingcavity therein and is spaced above the bottom of the chamber, the liquidoutlet including a conduit extending centrally of and into the cavity ofthe core member.

Means may also be provided for compacting the solid waste material to becharged in which case the core member desirably includes a substantiallyvertical gas passageway in the upper portion thereof communicating atthe ends thereof with the pyrolysis chamber, whereby the combustible gaswill detour through the gas passageway to thereby partially bypass thecompacted waste in the upper region of the pyrolysis chamber.

The disposal apparatus includes a substantially vertical prill chamberwith a gas outlet opening at the top thereof. A reservoir for moltenrefractory material, extending across an upper horizontal section of theprill chamber, has a plurality of vertical gas conduits extendingtherethrough and a plurality of molten refractory discharge orifices atthe base thereof. Conduit means conduct molten refractory material fromthe liquid outlet to the reservoir and means for introducing relativelycool gas into the prill chamber are disposed below the reservoir,whereby the gas rises through the droplets of refractory material toshape and partially cool the droplets into prills before passing throughthe vertical gas conduits and out the top gas outlet opening. Disposedin the prill chamber below the reservoir are means for receiving andcollecting the prills. In a preferred embodiment the collecting meansincludes a substantially funnel-shaped portion, and additionallyassociated with the prill chamber are means for introducing liquid intothe prill chamber and maintaining a thin layer of the liquid across thematerial-receiving surface of the funnel-shaped portion to further cooland cushion the impact of the shaped and partially cooled prills thereonand means for separating and separately discharging the liquid and theprills.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG.1 is a schematic view of a waste disposal system embodying thepresent invention;

FIG. 2 is an enlargement of the system of FIG. 1 circumscribed inphantom line;

FIG. 3 is a fragmentary elevational view of a reactor embodying thepresent invention, with portions thereof being broken away to revealinternal construction;

FIG. 4 is a schematic view of the burner and exhaust system located atthe base of the reactor in FIG. 3

FIG. 5 is a partially diagrammatic, fragmentary elevational view to areduced scale of the top portion of the reactor of FIG. 3 and theassociated charging mechanism, with walls broken away to reveal internalconstruction; and

FIG. 6 is a fragmentary, partially schematic elevational view in sectionof prilling tower, useful in the practice of the process of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Solid Waste Material

The refuse which may be utilized as the solid waste material feed stockis a mixture or organic and inorganic materials of the type obtainedfrom municipal rubbish and garbage collection, commercial and industrialwaste, waste from demolition and construction operations, etc., and willnormally contain as minimum values by weight, about 2.0 per cent ofglass and ceramics, 18.0 per cent of paper products, 3.0 per cent ofmetals, and 6.0 per cent of food waste and other miscellaneous organicmaterial. Although the composition of the refuse will vary dependingupon its source, a more specific breakdown will usually include paperproducts, glass, ceramics, moisture, tin cans, articles of iron, steeland other metals, natural and synthetic rubbers and resins, food wastes,oils, paints, chemicals (organic and inorganic), yard wastes, leathertextiles, wood, and inert materials. Refuse normally contains 15-30 percent by weight of water; typically the dry material is made up of 60 -95 per cent of volatile matter generally comprising the paper products,the natural organic materials and the synthetic resins, and thenonvolatile and relatively noncombustible components usually compriseabout 5 - 25 per cent of siliceous materials and up to about 15 per centof metals.

Refuse may, in addition, be analyzed on both a proximate and also anultimate basis, typical values for a proximate analysis of the drymaterial being about 40 - 80 per cent of volatile matter, 15 - 5 percent of fixed carbon and 45 - 13 per cent of ash and metal. On anultimate basis, typical dry refuse contains about 25 - 85 per cent ofcarbon, about 2 - 10 per cent of hydrogen, about 15 - 50 per cent ofoxygen, about 0.2- 1.5 per cent of nitrogen, 0 to about 1.0 per cent ofsulfur and about 5 - 35 per cent of glass, ceramic, stones, metals, ashand miscellaneous inert materials.

Although presently it is not generally necessary either to add to orextract from the refuse feed, in some instances it may be desirable tomodify the mixture with respect to various components. Moisture usuallyfound in the feed may be entirely removed or reduced, either as acontrol measure or to reduce the heating requirements of the system byavoiding the necessity of evaporating large amounts of water. On theother hand, it may be advantageous to introduce a quantity of water,particularly when a thermal decomposition technique is used, once againas a control factor or to influence the composition of the gas streamand/or the ceramic produced. Similarly, air may be added or removed fromthe material as a control mechanism and to affect the properties of theproducts, as will be more fully described hereinafter.

The refuse mixture may initially be treated in a magnetic separator toremove at least a portion of the ferrous content thereof, particularlyif the metal is present as undesirably large pieces. Moreover, due tothe increasing emphasis upon maximum utilization of mineral values, itis believed that such separation will in the near future assume greaterimportance than it has in the past. The heavy ferrous metal scrap mayadvantageously be separated for size alteration or for sale; the lighterferrous metal scrap may be beneficially employed in combination with theresidue in the production of certain types of metal-filled or reinforcedarticles.

The Process

Referring now to FIGS. 1 and 2, therein is schematically illustrated aprocess embodying the present invention. A garbage dump truck depositssolid waste material containing refuse of the type described hereinabovein a refuse receiving and storage building 12. A system of horizontaland inclined hinged steel belt conveyers 14 and 14', respectively,transports the refuse to the top of a refuse feed chute 16. As part ofthis stage of the process, metal removal, moisturizing orde-moisturizing and aerating of the refuse may be performed upon thematerial as it is being conveyed from the reception point to the feedhopper for the reactor. The solid waste material discharged from thefeed chute 16 drops into a feed conduit generally designated by thenumeral 18 and located at the upper end of the reactor generallydesignated by the numeral 20. Sealing means 22 are provided between thefeed conduit 18 and the chute 18 to minimize flow of gases from thereactor 20 therethrough and sealing means (not shown) are also desirablyprovided between the feed conduit 18 and the reactor 20 to minimize flowof gases from within the reactor 20 when the refuse is not being chargedinto the reactor 20.

As the charged refuse falls through the reactor 20, it successivelypasses through zones of differing temperature and successively undergoesfirst drying and limited combustion, then pyrolysis or decomposition ofits organic components and finally charring and oxidation to form amolten mass of metallic and other inorganic oxides. The structure of thereactor 20 and the process by which the charged refuse is converted intouseful products will be described in great detail hereinafter inconnection with a preferred reactor; however, it will suffice here torecognize that solid waste material charged into reactor 20 is convertedinto a combustible gas which rises into the upper region of the reactorand a molten refractory material which collects in the lowest region ofthe reactor. In this embodiment of the process, the molten refractorymaterial is discharged as slag 24 through the slag nozzle 26 and loadedonto slag buggies 28 for removal from the system or transported tofurther processing.

The combustible gas is removed through combustible gas outlet 30 intothe conduit 32 and is passed through a tar condensing and gas recoverysystem, generally designated by the numeral 34 and showndiagrammatically in FIG. 2, to remove the tars therefrom. The tarcondensation is effected in a tar condenser unit 36 by spraying thestream of combustible gas with a suitable liquid such as water andseparating the heavy tars which are condensed thereby from thecondensing liquid, conveniently by decanting. The combustible gas may bepassed to a gas recovery processing unit 38 wherein it is compressed andstored for future use or sale, or it may be transported to a combustionunit and heat exchanger generally designated by the numeral 40, andshown in FIG. 1. The manner in which the combustible gas is utilized isdetermined by the setting of a variety of valves and other controlmechanisms, the general object being to utilize the combustible gas inthe most efficient and economical manner possible.

A blower 42 forces an oxygen-rich gas such as air into an annularchamber 44 formed in the wall of the reactor 20 in the lower portionthereof, and this gas is preheated while it simultaneously cools thewall of the reactor 20 before it is conveyed by the conduit 46 to thecombustion unit and heat exchanger 40 where it mixes with thecombustible gas. Within the combustion unit 40, the hot gases are burnedand generate additional heat which is partially utilized to transferheat through the heat exchanger 48 located within the combustion unit40. A blower 50 directs an oxygen-rich pyrolysis gas such as air throughthe heat exchanger 48 and then through the gas conduit 52 to the coremember generally designated by the numeral 54 from which it isdischarged into the reactor 20 at a plurality of vertically spacedpoints. This pre-heated gas facilitates the controlled combustion andpyrolysis in the reactor 20 as will be discussed more fully hereinafter.

Alternatively, if the blower 32 is de-activated or if the conduit 46 isclosed off to the combustion unit 40 by a valve (not shown) oxygen-richgas will not be introduced into the combustion unit 40 and the unit willserve only as a heat exchanger. In this embodiment of the process, thehot combustible gases entering through the conduit 32 passing in heatexchange contact with the oxygen-rich gas being supplied to the coremember 54 by the blower 50. This hot combustible gas will then retainits fuel value and may, in fact, be passed in heat exchange contactprior to storage or utilization at a different installation.

In the illustrated embodiment of the process, the hot gases resultingfrom the combustion of the combustible gas in the combustion unit 40 maybe cycled through the conduit 56 to a heat exchanger generallydesignated by the numeral 58 in which they pass in heat exchange contactwith a suitable fluid medium (such as water) circulating through thecoils 60 to convert that fluid medium into a pressurized fluid mediumsuch as steam. The gases then exit through the conduit 62 and pass backto the main conduit 64. A valve 66 is provided in the main conduit 64 tocontrol the flow of the hot combustible gases directly through the mainconduit 64 or to the heat exchanger 58 through the conduit 56 by openingthe valve 68 therein.

As the gases are moved through the conduit 64 towards discharge underthe action of the blower 70, they may be cooled by the injection ofwater through the water injector 72 and they may be passed throughparticulate removal apparatus (not shown) prior to discharge through thestack 74. The resultant gases will thus be free of particulate matterand are comprised of essentially non-polluting components (carbondioxide, oxygen, nitrogen and water vapor) which may be discharged tothe atmosphere.

In the event that combustion of the combustible gas has not taken placein the combustion unit 40, the hot combustible gas may, nevertheless, bepassed through the heat exchanger 58 depending upon the thermal gradientwhich then exists across the heat exchanger, or it may be funneledthrough the conduit 64 to a compressor and storage tank (not shown) forlater use or sale.

In the heat exchanger 68 the water passes through the coils 60, isconverted to steam under pressure and is conducted through the conduit76 to the steam turbine 78 producing drive energy for the generator 80which, in turn, results in power designated by the block 82. The spentsteam exits from the turbine 78 through the conduit 84 and passes to thecooling tower generally indicated by the numeral 86 in which it givessome of its heat up as it passes through the coils 88. The now cooledsteam may be discharged if so desired or it may be recycled through thesystem. Additional makeup water is introduced into the conduit 92through the pump 90 and passes through the coils 60 to complete theloop.

Preferred Reactor

Turning now in detail to FIGS. 3-5 of the drawings, therein illustratedis a preferred reactor/refuse compactor design. The reactor 20 isgenerally similar to that illustrated in FIG. 1 and is adapted to beemployed in the overall process described with respect to FIGS. 1 and 2.

The reactor has a base or platform portion 100 and a dome portion 102,and a generally cylindrical, vertical sidewall, generally designated bythe numeral 104, extends therebetween. As best seen in FIG. 3, thesidewall 104 includes a relatively thick concrete outer shell 106; andintermediate insulating layer 108 of alumina or the like, and an innerrefractory brick lining 110. At the bottom of the reactor 20 over thebase 100 are provided a floor plate 112, an annular heater unit 114therebelow and refractory bricks 116 therebetween and thereabout.Extending through an aperture in the floor plate 112 the centralaperture in the annular heater unit 114, the refractory bricks 116 andan aperture in the base 100, is an elongated discharge tube 118 whichprojects into the reactor chamber 101 and opens at a point spaced abovethe floor plate 112. Gas burners 120 to which a combustible fuel gas andair are supplied produce hot gases introduced into the heater unit 114through the conduits 122 to effect heating of the floor plate 112 andthereby the contents of the reactor 20. The hot gases are dischargedthrough the exhaust conduits 124.

Supported coaxially within the reactor chamber 101 is the core member 54which extends from a point somewhat below the upper end of the dischargetube 118 and is supported upon the floor plate 112 by the spacer members126, thus providing a baffled path from the main portion of the reactorchamber 101 to the inlet end of the discharge tube 118. The core member54 is of generally cylindrical configuration and has a sidewallcomprised of a high temperature alloy steel element 126 and an aluminaouter shell 130. Extending transversely of the interior of the coremember 54 are four wall members 132, 134, 136, 138, defining plenumchambers 140, 142, 144 therebetween. A multiplicity of dischargeorifices 146, 148, 150 are provided in the sidewall of the core member54 in each of the several plenum chambers 140, 142, 144, and are angleddownwardly for discharge of air introduced thereinto outwardly into themain portion of the reactor chamber 101. Each of the plenum chambers140, 142, 144 is separately fed by a heated air conduit 152, 154, 156respectively and, as seen in FIG. 5, the volume of air to each of theseveral conduits may be regulated by the valves 158, 160, 162.

At its upper end, the core member 54 is closed by the top wall 164.Supported on the top wall 164 by spacer members (not shown) and upon theconduits 152, 154, 156 by spacer members (not shown), is a gas bypasstube 166 which is of a length sufficient to extend above the normallevel of refuse introduced into the reactor chamber 101. A top deflector167 is spaced above the upper end thereof and supported upon the heatedair conduits 152, 154, 156 so as to deflect refuse from the opening intothe gas bypass tube 166. In this manner, gases being produced within thelower portion of the reactor chamber 101 may pass into and upwardlythrough the gas bypass tube 166 and thence outwardly therefrom above thelevel of the relatively compact refuse in the upper portion of thereactor chamber 101 through which its flow would be substantiallyimpeded. These gases then enter into the upper portion of the reactorchamber 101 and are discharged through the combustible gas conduit 32.

Located in the recesses at spaced points along the height of thesidewall 104 are a plurality of thermocouples 168 for sensing thetemperature therein and other thermocouples (not shown) are disposed inthe alumina shell 130 of the core member 54. A valve 170 is provided inthe discharge tube 118 to control flow of molten refractory materialtherethrough.

Turning now in detail to FIG. 5, therein partially schematicallyillustrated is a preferred refuse feed conduit and compactor design. Therefuse feed conduit 172 extends into the reactor 20 adjacent the upperend thereof and its inner end has a sealing member 174 pivotablysupported thereon. Refuse carried by the conveyor 14 is dropped into thehopper 176 and thence into the feed conduit 172. Movement of the refusefrom the hopper 176 into the body of the feed conduit 172 is assisted bythe crammer assembly generally designated by the numeral 178 whichincludes a plate 180 reciprocated by the piston 182 operating in thecylinder 184.

The refuse introduced into the feed conduit 172 is compacted by the ramassembly generally designated by the numeral 186. The ram head 188 isrelatively massive and snugly fits within the feed conduit 172 so as tominimize the likelihood of refuse extending about the sides thereofduring the compacting operation. It is provided with a cutout 190 in itsupper forward face which provides a relief point during the compactingoperation and minimizes the likelihood of jamming of the ram assembly186 during the compacting operation. The ram head 188 is driven by anelongated piston 194 operating within a cylinder (not shown) so that itwill compact refuse within the feed conduit 172 and also cause thecompacted refuse to move along the length of the feed conduit 172, pivotthe sealing member 171 and discharge into the upper end of the reactorchamber 101.

The Prilling Unit

Turning now in detail to FIG. 6, therein illustrated is a prilling unitwhich may be used for the production of ceramic beads from the moltenceramic material produced in the reactor 20 as compared with the processshown in FIG. 1 wherein a ceramic slag is taken away in slag buggles. Inthis particular embodiment of the process, the molten ceramic materialfrom the discharge tube 118 of the reactor 20 in FIG. 3 is conveyedthrough a conduit 200 to the prilling unit generally designated by thenumeral 202.

The prilling unit 202 is comprised of a generally cylindrical shell 204having a sidewall 206, top wall 208 with an exhaust duct 210 therein anda bottom wall 212. A funnel member 214 is disposed in the lower portionthereof and has a discharge tube 216 extending through the bottom wall212.

At the upper end of the shell 204, high temperature refractory-coated,perforated plate 218 is located having a multiplicity of orifices 220therein through which the molten ceramic material introduced thereabovemay be discharged as indicated by the arrows. In addition, theperforated plate 218 seats the lower end of high temperature refractorygas tubes 222 which have their upper ends seated in the heater plate 224spaced thereabove to define the feed chamber 226 therebetween into whichthe molten ceramic material is introduced.

Air is introduced into the shell 204 at a plurality of points spacedthereabout through the conduits 228 and this air passes upwardly throughthe shell 204, into the gas tubes 222 and is ultimately discharged fromthe plenum chamber 230 above the header plate 224 through the exhaustduct 210. Water is introduced into the funnel member 214 at a pluralityof points spaced thereabout through the multiplicity of conduits 232,and it flows downwardly over the surface of the funnel member 214 toeffect cooling thereof. The prills which are formed in the prilling unit202, together with the water, exit through the discharge tube 216 andare passed into a sprayer unit schematically indicated by the block 234in which there is effected the separation of the ceramic beads and theprocess water.

Operation of the Illustrated Embodiments

During startup, a special procedure is desirably employed so that theceramic product withdrawn from the reactor may have the same generallystable composition and characteristics as will be produced during normaloperation. To do so, a mass of the previously produced ceramic materialin solidified form is introduced into the base of the reactor chamber101 to a level somewhat below the level of the transverse wall 138 inthe core member 54. The valve 170 in the discharge tube 118 is closedand the burners 120 are ignited. In doing so, the fuel gas supplied tothe burners can be combustible gas produced previously and stored forutilization as fuel. Compacted refuse is charged into the upper portionof the reactor chamber 101 and settles upon the ceramic material whichhas been previously introduced.

After the temperature of the ceramic material in the bottom portion ofthe reactor chamber 101 has reached a predetermined minimum (usuallyabout 1075° Centigrade), the flow of oxygen-rich gas is begun to theseveral heated air conduits 152, 154, 156 with the volume to each of theplenum chambers 140, 142, 144 being regulated by means of the valves158, 160, 162. This will commence combustion and pyrolysis of theorganic materials present in the refuse charged to the reactor 20 and,after the temperatures in the several reactor zones have reached thedesired minima, the valve 170 may be opened and normal operation of thereactor begun with the molten ceramic material overflowing into thedischarge tube 118.

During normal operation, the solid waste material carried by theconveyor 14 is dropped into the hopper 176 and is crammed into the feedconduit 172 by the crammer assembly 178. The refuse thus deposited iscompacted by operation of the ram assembly 186 and is advanced along thelength of the feed conduit 172 until it pivots the sealing member 174and drops into the upper portion of the reactor chamber 101. Normally,the waste is sufficiently compacted so that it will minimize thelikelihood of combustible gases from the reactor chamber 101 exitinginto the refuse feed conduit 172 but the sealing member 174 is valuableas a gas seal during shutdown of the unit when there is no longer areservoir of compactd refuse in the feed conduit 172.

The compacted refuse thus spreads itself about the upper portion of thereactor chamber 101 and is deflected from entering into the gas bypass166 by the top deflector 167. As it is heated within the reactor chamber101, it will tend to fluff out and moisture will be rapidly evolved.

As will be appreciated, the withdrawal of the molten ceramic materialfrom the base of the reactor chamber 101 through the discharge tube 118and the combustion or volatilization will cause the refuse charged toslowly descend through the reactor chamber 101. Following the initialevolution of moisture, the organic material will reach a temperaturewhere, in the presence of oxygen-rich gas being introduced into theplenum chamber 140, combustion will begin with evolution of heat. Sincethe amount of oxygen-rich gas being furnished is being controlled toavoid complete combustion, this combustion will result in the productionof a combustible gas which will pass upwardly through the reactorchamber 101 and bypass the relatively compact refuse in the upperportion of the reactor chamber 101 by entering and moving upwardlythrough the gas bypass tube 166. The combustible gas and moisture whichis evolved will then exit from the reactor chamber 101 through thecombustible conduit 32 for further processing as has been describedhereinbefore with respect to FIGS. 1 and 2. Generally, the temperatureof the combustible gas adjacent the conduit 32 is about 250° to 550°Centigrade and preferably about 275° to 425° Centigrade.

As has been indicated, oxygen-rich gas which is preheated to the desiredcontrolled temperatures is being introduced to each of the severalplenum chambers 140, 142, 144 and the volume and temperature thereof arecontrolled so that predetermined temperatures are maintained within theseveral zones of the reactor chamber 101 as may be determined by thethermocouples 168 located in the reactor wall 104 and core member 54.This control may be effected automatically by means of conventionalanalog control mechanisms, or manually if so desired. Optical pyrometersmay also be used.

Generally, the temperature in the top or drying and initial combustionzone, which is disposed above the wall member 134 in the core member 54,is the zone of lowest temperature and into which proportionately theleast oxygen rich gas is introduced. The temperature of this zone ismaintained at about 375° to 750° Centigrade and preferably at about425°-600° Centigrade. The middle or pyrolysis zone is one ofintermediate temperature on the order of about 550° to 1075° Centigradeand preferably about 700° to 925° Centigrade. It generally occupies thearea above the wall member 136 in the core member 54 and below thedrying and initial combustion zone. In this zone, the supply ofoxygen-rich gas is again controlled so as to avoid complete combustionand to generate a combustible gas. Below this intermediate zone is thecomplete combustion and slag zone in which there is provided arelatively high volume of oxygen-rich gas to ensure complete combustionof any remaining organic materials and oxidation of any metallicmaterials into a molten ceramic. The temperature in this zone ismaintained at about 1075° to 1650° Centigrade and preferably at about1100° to 1300° Centigrade. In the lowest portion of the reactor whichcould be considered a portion of the complete combustion and slag zone,develops a pool of relatively pure and homogeneous molten ceramicmaterial which flows under the lower end of the core member 54 andthence into the discharge tube 118.

Generally, for every part by weight of refuse introduced into thereactor, about 0.5 to 2.0 parts by weight of oxygen-rich gas must beintroduced into the reactor chamber 101 through the core member 54 andpreferably this amount will be about 0.8 to 1.5 parts depending upon theexact composition of the refuse, the temperature of the oxygen-rich gasand the temperature desired within the several reactor zones. Thisamount of oxygen-rich gas is divided among the several conduits 152,154, 156 by means of the valves 158, 160, 162 so that the volumesupplied to the upper plenum chamber 140 will comprise about 10 to 25percent by weight of the total. The volume channeled to the intermediateplenum chamber 142 will comprise about 15 to 35 percent by weight andthat conveyed to the lowest plenum chamber 144 will comprise about 25 to60 percent.

As will be appreciated, the discharge orifices 146, 148, 150 are angleddownwardly from the horizontal to avoid channeling of the oxygen-richgas directly through the refuse toward the sidewall 104 and thusminimizes the likelihood of burning out. This angling also ensuresthorough distribution of the oxygen-rich gas throughout the annularreactor chamber 101 about the core member 54. The discharge orifices 146are preferably at an angle of about 40° to 50° to the vertical axis ofthe core member 54, the discharge orifices 150 are preferably at anangle of about 55°-60°, and the discharge orifices 148 are preferably atan intermediate angle.

This effective division of the reactor chamber into three independentlycontrollable temperature zones to which oxygen-rich gas is fed centrallyenables close control of the pyrolysis of the organic components toproduce a combustible gas of desired value and ensures that the ceramicmaterial will be completely removed from the organic material when it isremoved from the reactor. Moreover, it can be seen that all metalliccomponents are oxidized to form the molten ceramic.

In accordance with a preferred embodiment of the process, the moltenceramic material exiting through the discharge tube 118 is conveyedthrough the conduit 200 to the prilling unit 202. It drips through theorifices 220 in the perforated plate 218 to form small droplets whichthen fall downwardly within the central chamber of the prilling unit202. As the droplets fall, they are controlled by air which is passingupwardly in countercurrent flow and which has been introduced into thechamber of the prilling unit 202 through the conduits 228. As a result,the molten ceramic droplets harden and solidify into generally sphericalceramic prills which then drop onto the surface of the funnel member 214over which is flowing a stream of water introduced through the waterconduits 232. This water flow further cools the prills and minimizes theimpact forces and also serves to cool the funnel member 214. The mixtureof prills and water is then discharged through the discharge tube 216and passes to the separator 234. This may be a conventional decantingtype mechanism, a centrifuge or the like in which the beads or prillsare separated from the process water which then can be recirculated.

Although the composition of the ceramic product may vary, typically itcontains, on a weight basis, about 20-70 percent of silicon dioxide,about 5-30 percent of aluminum oxide, about 5-20 percent of alkall metaloxides, about 1-20 percent of calcium oxide, about 1-30 percent of ironoxide, a trace to about 10 percent of magnesium oxide, a trace to about5 percent of tin oxide, and trace amounts of lead, copper, barium,titanium, zinc and miscellaneous other metal oxides. The residue willnormally also contain small amounts of dissolved gases, sulfur compounds(e.g., sulfates), etc. The properties of the ceramic material generallywill not vary a great deal with refuse composition, and some controlthereof can be obtained by varying the dissolved volatiles (e.g., water)and the atmosphere during fusion. Generally, the ceramic material has arelatively high coefficient of thermal expansion and a specific gravitynormally in the range of about 2.3-3.5, it has a relatively lowviscosity and, when solidified, will deform under its own weight at aslow as 550°Centigrade. Compared to typical container glass compositions,the viscosity of the ceramic material of the present invention atelevated temperatures is much lower, its coefficient of expansion ishigher, and it softens at temperatures significantly below that of suchglass.

As indicated hereinbefore, the combustible gas which is exiting throughthe conduit 32 is passed through the combustion unit 40 wherein it isadmixed with additional oxygen-rich gas and burned to generate heat.This heat is used to raise the temperature of air or other oxygen-richgas passing through the heat exchanger 48 and used to supply the severalheated air conduits 152, 154, 156 supplying the several plenum chambersof the reactor 20. The oxygen- rich gas is preferably heated to atemperature of at least 30° Centigrade and up to about 825° Centigradedepending upon the reactor conditions required. Generally, andpreferably, the temperature of the oxygen-rich gas being introduced intothe reactor 20 will be about 275° to 550° Centigrade.

Other aspects of the operation of the process have been describedhereinbefore with respect to the description of FIGS. 1 and 2 of thedrawings.

Depending upon the type of refuse charged and the operating conditionswithin the reactor, the combustible gas within the reactor will includewater vapor, carbon monoxide, hydrogen, low boiling organic fractions,nitrogen and some entrained solid particulate material. It may containorganic tars which desirably are recovered as a by product of theprocess as indicated in FIG. 2 by passing the combustible gas through atar condenser.

When required, the burners 120 may be operated to maintain the desiredheat level within the reactor chamber 101 and thus they too may besubject to automatic control through an analog device.

As previously indicated, the oxygen-rich gas introduced to the upperportion of the reactor chamber or upper zone may vary from as little as10 percent of the total input to as much as 25 percent. Since theprimary input of oxygen-rich gas is required at the lowest zone andsince only drying and limited combustion are required in the upper zone,the preferred percentage of oxygen rich gas directed into the upper zonewill be about 10 to 15 percent. Since pyrolysis occurs in theintermediate zone, about 15 to 35 percent of the oxygen-rich gas isintroduced into this zone. Under normal conditions, the preferredpercentage will be 15 to 25 percent. As is readily apparent, it isessential that there be adequate oxygen-rich gas in the lowest zone toeffect complete combustion of any remaining organics and to generate theheat necessary to convert any metals into oxides and to melt all oxidesinto a molten refractory material. As a result, the oxygen rich gas fedto the lowest zone will normally comprise 25 to 60 percent andpreferably about 45 to 60 percent of the total input.

As has also been indicated previously, the oxygen-rich gas is desirablypreheated so as to facilitate drying, combustion and pyrolysis withinthe reactor. However, in some instances it may be desirable to useambient air in order to retard combustion occuring in one or more of thezones. However, for normal operation, the oxygen-rich gas will bepreheated to temperatures from 30°to 825° Centigrade and preferablyabout 275° to 550° Centigrade.

Illustrative of the efficacy of the waste disposal system of the presentinvention is the following example in which all parts are by weightunless otherwise indicated.

EXAMPLE

The reactor used herein is similar in design to that shown in FIGS. 3-5and has a height of 7.3 meters and an inside diameter of 2.4 meters. Theouter surface of the sidewall is 22 cm thick reinforced concrete and theinside surface is provided by 15 cm thick refractory brick lining with a5 cm thick insulation therebetween of alumina. The core member in thereactor has a 0.3 meter inside diameter and a 7 cm thick coating ofalumina insulation. The base plate of the pyrolysis chamber, and theinside layer of the core member and of the molten ceramic discharge tubeare composed of a nickel/steel alloy capable of withstanding extremelyhigh temperatures and sold under the trademark INCOLOY 300 by TheInternational Nickel Company.

The upper 2.4 to 3.0 meters of the reactor include the refuse charginginlet and combustible gas outlet and serve as the drying and initialcombustion zone. The next lower 1.8 to 2.4 meters serve as the pyrolysiszone with the next lower 1.2 to 1.8 meters serving as the completecombustion and siag forming zone. The bottom 0.4 to 0.8 meters areoccupied by the slag reservoir, the burner and exhaust system and thereactor base.

The reactor is started up by closing the molten ceramic discharge tubeand introducing ceramic material previously produced by the subjectprocess into the pyrolysis chamber. The burners are ignited usingcombustible gas previously produced by the subject process and solidwaste material is charged into the chamber. When the temperature of theslag reaches 1100° C and combustion aand pyrolysis are maintaining thedesired heat levels in the several zones, the burners are switched tostand-by status for activation only if the slag temperature drops below1100° C, and the molten residue drain pipe is opened.

In the regular course of operation, solid waste materials are fed intothe feed hopper at a rate of about 4500 kilograms per hour. The refuseis vibrated into a 1 meter by 1 meter feed chute by a crammer orvibrating plate and compacted to one-third of its volume as the main ramwhich is rated to deliver a pressure of 2.1 kilograms per squarecentimeter reciprocates over a length of 1.5 meters within the feedchute at about 1 cycle per minute.

The charged material falls into the drying and intial combustion zonewhere the temperature is maintained at 425° to 600° C. In this zone,most of the water vapor is driven off and some of the organic matterundergoes initial combustion. The charge slowly continues its descentthrough the chamber and passes into the pyrolysis zone, where thetemperature is maintained at 700° to 925° C. In this zone which has asupply of oxygen-rich gas insufficient to produce complete combustion,the organics decompose and volatilize. The remnants of the charge slowlydescend into the slag and complete combustion zone where the temperatureis maintained at 1100° to 1300° C. In this zone, where an excess ofoxygen is provided, the metals are oxidized and the char is burned offto provide an essentially homogeneous molten ceramic slag phase in thebase of the reactor chamber which overflows into the ceramic dischargetube.

The various gases produced within the reactor chamber are removed as acombustible gas stream through the combustible gas outlet where thetemperature is about 275° to 425° C. The removed combustible gases areintoduced into a combustion chamber which is supplied with excessamblent air. The combustible gas undergoes further combustion at thispoint without further assistance, the temperatures within the combustionchamber rising, as a result of this combustion, to about 1000° to 2000°C depending upon the caloric value of the gas.

Air to be introduced into the reactor chamber is preheated by passagethrough a heat exchanger locatd within the combustion chamber, the airtemperature being about 275° to 550°C upon exiting from the heatexchanger. The heated air is then distributed to the various pyrolysisair conduits in relative proportions according to the settings of theconduit valves, which are in turn determined by the thermocouples withinthe reactor. About 0.8 to 1.5 parts by weight of heated air areintroduced into the reactor for every part by weight of refuse beingintroduced, the heated air being distributed among the pyrolysis gasconduits so as to effect the temperature zones hereinabove described.

The combustion products and volatiles withdrawn from the combustionchamber are further utilized to heat water in a steam generator beforebeing scrubbed and exhausted.

Thus it can be seen from the foregoing detailed specification, drawingsand example that the present invention provides a novel method andapparatus for disposing of solid waste material and obtainingsubstantially pure refractory material and combustible gas as productsthereof. The method is highly economical as a result of relatively lowoperating costs and the high utilization of component fractions in therefuse, and the apparatus enables close control of the pyrolysistreatment obtain maximum available energy from the refuse.

We claim:
 1. Apparatus for disposing of solid waste comprising:A. areactor having a shell providing a substantially vertical pyrolysischamber, a charging inlet and a gas outlet in the upper region thereofand a liquid outlet in the lower region thereof; B. means for chargingsolid waste material having organic and inorganic components throughsaid charging inlet; C. gas-feed means for charging an oxygen-rich gasinto said chamber under pressure at a plurality of vertically spacedpoints along the length thereof so as to produce combustion of the wasteorganic components and generate heat; D. means for controlling thecharging of the oxygen-rich gas at each of said plurality of verticallyspaced points to maintain a plurality of different temperature zonesalong the length of said chamber so as to effect incomplete combustionof the waste organic component and form a combustible gas and anorganic-free molten refractory material whereby the combustible gas isremoved through said gas outlet and the molten refractory material isremoved through said solids outlet; and E. prilling means incommunication with said solids outlet for prilling the molten refractorymaterial.
 2. The apparatus of claim 1 wherein said gas-feed meansincludes a substantially vertical coaxial core member within saidchamber to receive the oxygen-rich gas, said core member having portsadjacent said plurality of vertically spaced points for discharge of theoxygen-rich gas therethrough.
 3. The apparatus of claim 1 additionallyincluding a combustion chamber;heat exchange means in said combustionchamber for passage of a fluid medium therethrough; means for conductingthe removed combustible gas from said gas outlet to said combustionchamber means for admixing oxygen-rich combustion gas with saidcombustible gas; and means for combusting the removed combustible gasand the oxygen-rich combustion gas in said combustion chamber to heat afluid medium in said heat exchange means to provide said means forpreheating.
 4. The apparatus of claim 3 additionally including means forpassing oxygen-rich gas through said heat exchange means as the fluidmedium and a conduit from said heat exchanger to said gas-feed means,whereby the heat produced by the combustion heats the oxygen-rich gasprior to the discharge thereof into said pyrolysis chamber.
 5. Theapparatus of claim 1 additionally including a heat exchanger a conduitfrom said gas outlet to said heat exchanger for passing the removedcombustible gas therethrough; a conduit from said heat exchanger to saidgas feed means whereby the gas may be passed therethrough in heatexchange contact with combustible gas for heating prior to its dischargethereof into said pyrolysis chamber to provide said means forpreheating.
 6. The apparatus of claim 1 additionally including burnermeans adjacent the base of said chamber.
 7. The apparatus of claim 2wherein the bottom end of said core member has a downwardly openingcavity chamber therein and is spaced above the bottom of said chamberand wherein said liquid outlet includes a conduit extending centrally ofand into said cavity of said core member.
 8. The apparatus of claim 1wherein said prilling means comprises:A. a substantially verticalelongated prill chamber with a gas outlet opening at the top thereof; B.a reservoir for molten refractory material extending across an upperhorizontal section of said prill chamber and having a plurality ofvertical gas conduits extending therethrough and a plurality of moltenrefractory discharge orifices in the base thereof; C. conduit means forconducting molten refractory material from said liquid outlet to saidreservoir; D. means for introducing gas into said prill chamber belowsaid reservoir, whereby the gas rises through the droplets of refractorymaterial to shape and partially cool the droplets into prills beforepassing through said vertical gas conduits and out said gas outletopening; and E. means in said prill chamber disposed below saidreservoir for receiving and collecting the prills.
 9. The apparatus ofclaim 8 wherein said collecting means includes a substantially funnelshaped portion and said prilling means includes additionally includesA.means for introducing liquid into said prill chamber and maintaining athin layer of the liquid across the material-receiving surface of saidfunnel shaped portion to further cool and cushion the impact of theshaped and partially cooled prills; and B. means for separating andseparately discharging the liquid and the prills.